A fuel cell includes an anode, a cathode, and an electrolytic membrane interposed therebetween. The fuel cell generates electric power using an anode gas containing hydrogen supplied to the anode and a cathode gas containing oxygen supplied to the cathode. An electrochemical reaction generated in both the anode and the cathode can be expressed as follows.Anode: 2H2→4H++4e−  (1)Cathode: 4H++4e−+O2→2H2O  (2)
Through the electrochemical reaction of Expressions (1) and (2), the fuel cell generates an electromotive force of, approximately, 1 V.
When the fuel cell is employed as a power source of a vehicle, a fuel cell stack obtained by stacking several hundreds of fuel cells is used. In addition, a fuel cell system capable of supplying an anode gas and a cathode gas to the fuel cell stack is provided to output electric power for driving a vehicle.
In such a fuel cell system, a coolant circulation path is provided to cool the fuel cell stack. If the fuel cell system is used for a long time, an impurity ion such as Na+ or SO42− is eluted to the coolant from a pipe or the like of the circulation path, so that electric conductivity of the coolant increases, and power generation performance of the fuel cell stack is deteriorated. For this reason, an ion exchanger for removing an impurity ion from the coolant is provided in the coolant circulation path. In the ion exchanger, it is preferable that an ion exchange rate relating to impurity ion removal performance be high and a pressure loss which is a pressure difference between an inlet side and an outlet side be small.
JP 2009-219954 A discloses a dual channel structure ion exchanger having an inner pipe and an outer pipe. In this ion exchanger, one of a path formed inside the inner pipe and a path formed between the inner and outer pipes serves as an ion exchange path filled with an ion exchange resin, and the other path serves as a bypass path.